1. Field of the Invention
This invention relates to pre-foamed particles of a polyethylene resin, and more specifically to pre-foamed polyethylene particles suitable for use in the production of expansion-molded polyethylene articles excellent in both elongation and flexibility.
2. Description of the Prior Art
Expansion-molded polyethylene articles obtained by subjecting pre-foamed particles of a polyethylene resin to expansion molding have found wide-spread commercial utility as cushioning materials, heat-insulating materials, surface-protecting materials and miscellaneous other goods. Pre-foamed particles which have heretofore been employed for the production of molded articles of the above sort use, as base resins, branched polyethylene resins having long branch chains. Since it is necessary to adjust the melt viscosity of each of such base resins within a range suitable for its pre-foaming upon production of pre-foamed particles, the pre-foamed particles are imparted with a crosslinking degree as high as 50-70% in terms of gel content. For this reason, expansion-molded articles obtained eventually by using such pre-foamed particles were accompanied by a drawback that they were inferior in elongation, although they had good flexibility. As methods for improving such a drawback, it has been proposed to obtain an expansion-molded article by using a polyethylene-base resin the density and Vicat softening point of which fall within certain specific ranges (Japanese Patent Laid-Open No. 82828/1981), to obtain an expansion-molded article by using a polyethylene-base resin the melting point of which falls within a certain specific range (Japanese Patent Laid-Open No. 70621/1982), etc.
Expansion-molded articles obtained by these methods are however accompanied by a drawback that they are lowered in flexibility although they are improved in elongation. It is hence still difficult to obtain expansion-molded polyethylene articles excellent in both elongation and flexibility.